1. Technical Field of the Invention
The present invention comprises the recovery of precious and heavy metals from spent catalyst materials.
2. Prior Art
The present invention comprises a furnace system for recovering precious and heavy metals from spent catalysts. Precious metal catalysts such as platinum, palladium and rhodium, and heavy metal catalysts such as nickel, cobalt and molybdenum are used in various industries such as the petrochemical industry, petroleum refining industry and the soap and detergent industry. Further, automobiles use catalytic converter pollution control devices which contain precious metal catalysts such as platinum, palladium and rhodium. These catalysts are generally employed in the form of supported catalysts wherein the metal is carried on the surface of a support or carrier composed of an inorganic ceramic material of an oxide such as aluminum oxide, silicon oxide, magnesium oxide, calcium oxide, zirconium oxide, or combinations thereof. The precious and heavy metals which may be recovered from these catalysts are valuable and the metals recovered therefrom may be recycled to produce new catalysts.
U.S. Pat. No. 4,337,085 and 4,349,381, both assigned to Kennecott Corporation, disclose a process for recovery of precious and heavy metals from spent catalysts. Both patents disclose a spent catalyst furnace which may be an electric furnace of the arc type; however, other furnaces such as reduction or resistance electric furnaces are disclosed as alternatives. The patents are directed to the method of heating the spent catalyst in a spent catalyst furnace and then transferring the recovered alumina from the spent catalyst to an abrasive or refractory furnace for treatment with other materials to recover fused alumina. Both patents disclose the preferred method as making numerous pourings of the molten alumina from the spent catalyst furnace for transport to the abrasive or refractory furnace in a hot slag ladle or in a trough prior to the final deep pour to recover the precious or heavy metal from the spent catalyst furnace. The deep pour is into a mold or ladle wherein the materials are cooled, and then the precious or heavy metal recovered from the alumina after being broken apart and separated.
A process is disclosed in U.S. Pat. No. 4,334,924 for the recovery of molybdenum from a spent catalyst. A concentrated or enriched matte or alloy is recovered from a reverberatory furnace in a continuous operation in a furnace or ladle. This iron sulfide matte, which connotes a predominantly sulfide material, or alloy, which connotes a predominately metallic material which may contain sulfur, is enriched by oxidizing the molten matte or alloy with air or oxygen in the furnace or ladle. It is disclosed that the oxygen is introduced through an oxygen lance. In this process the sulfur which is in the enriched molybdenum matte or alloy is oxidized so that the sulfur is removed in the form of gaseous sulfur oxides.
U.S. Pat. Nos. 4,427,442 and 4,428,768 discloses a method for the recovery of precious metals such as spent catalysts. This process is carried out in a plasma arc furnace. A molten metallic phase and a slag phase are formed in the plasma arc furnace and these two phases are separated so that the precious metal can be recovered from the metallic phase.
The present invention overcomes the deficiencies of the prior art apparatus and processes. None of the foregoing patents disclose a simple apparatus for recovering precious metals and the present invention provides an improved furnace system for efficiently separating precious and heavy metals from spent catalysts.
Other objects and advantages of the invention will appear from the following description.